Buying Gasoline

mikeBOS · Post by **mikeBOS** » Tue Mar 22, 2011 8:35 pm

I have a car right now. In order to limit the time and inconvenience of refueling I always drive until I've only got about a gallon of fuel left, and then I fill the tank.
Now, I have several friends, my own parents, and it seems most of the other people I see buying gas, who I notice rarely fill up. Instead they spend $10 here, $20 there, apparently because if they fill up they feel like they're spending more money on fuel.
Of course, they're still spending the same amount, just in smaller, more frequent payments. In fact, they're probably spending just a little bit more if you count the time it takes to stop at a fueling station, plus the additional driving out of their way they have to go to get to fueling stations more often.
For the people I know, cash flow isn't the issue, they have the money in the bank available to fill up, they just can't handle parting with it all at once.
It has always seemed to me to be a perfect example of irrational, emotionally-based, financial decision-making. Is there any reason, that I'm not seeing, not to fill up the tank in a vehicle you're driving regularly?

George the original one · Tue Mar 22, 2011 8:42 pm

Only if I suspect fuel prices are coming down within the week would I not fill up. Fuel prices are NOT going to come down that soon.
Wife was trained by her dad to not let it get below 1/4 tank so that there's fuel in case of an emergency. Of course they also lived 5+ miles from the nearest gas station and 20 miles out of the big city.

mikeBOS · Post by **mikeBOS** » Tue Mar 22, 2011 9:27 pm

The weight issue I hadn't considered. I suppose that is an advantage. Though, you'd have to offset it against the cost of braking, pulling into the station, shutting off and then restarting the vehicle and getting back up to speed.
Of course, these are people who, like most drivers, rarely check their tire pressure, keep junk in their trunk and have probably never heard of hyper-miling, so I don't think reduced weight is their motive.
But that would at least be rational if that was their motive. What I was trying to get at more though is the irrationality of the issue. - People choosing to trick themselves to make them feel better rather than actually siting back and analyzing their habits to decide what would make the most sense.

Sven · Post by **Sven** » Tue Mar 22, 2011 10:35 pm

Probably that is not done by the majority of those people you see doing it, but there might also be people doing something like dollar cost averaging at the gas station (at least i heard some people are actually doing that).

mikeBOS · Post by **mikeBOS** » Tue Mar 22, 2011 10:52 pm

Just being that price-conscious about this one product seems strange too.
These are people who will drive across town to save $2 on a tank of gas while driving a financed, brand new SUV and sipping a $4 latte.
They flippantly spend money everywhere but when it comes to buying fuel they're suddenly a more price-conscious miser than I am

Matt · Post by **Matt** » Tue Mar 22, 2011 11:22 pm

Same attitude that makes people want to pay their car or home insurance monthly instead of annually or bi-annually. Even if it doesn't save me a penny, I'd rather only pay once or twice a year and not have to think about it again. But, some people can't bear to drain that much cash and would rather break it up.

Post by **jacob** » Tue Mar 22, 2011 11:34 pm

I used to track oil prices on a day to day basis and pump prices would typically lag those by a couple of days.
Coordinating this won't save much unless the gas station is on your way.
There's also the risk of not having a full tank, e.g. hurricane takes out a couple of refineries or choke points. Or maybe more relevant you get stuck in your car in a snow storm due to some traffic accident and the only thing between you and a deep freeze experience is the gas that keeps the engine idling. (Happened to us in Wyoming once during a snow storm. We sat there for 5-6 hours before the road was cleared from the multiple big-rig crash.)

mikeBOS · Post by **mikeBOS** » Tue Mar 22, 2011 11:36 pm

I'm with you Matt. I hate monthly payments. I pay all my insurance up front 12 months at a time and get a discount for it. I even pay my phone bill a year in advance.
It's nice not to have to think about any of that stuff for 364 days a year.

halcyon · Post by **halcyon** » Tue Mar 22, 2011 11:44 pm

I highly doubt this is the reason but I read that you get more actual fuel if you refuel when you are around half empty. The reason being then when you fill an empty tank, more of the gas becomes vapors and is recaptured by the pump. The same can be said about filling up in the morning vs the afternoon. The gasoline in the underground tank is cooler and so more of it is liquid and less is vapor.
Again, I think it's more the psychological factor of dropping all that money at once to fill up your gas guzzler. I think most people feel that driving is a necessity and so they are hyper concerned when costs that the *have* to pay go up. You can *choose* to buy a $4 latte, for some people they feel they can't choose not to drive.

chilly · Post by **chilly** » Tue Mar 22, 2011 11:50 pm

There is one viable argument for not letting it get too low. In colder climates you could be more prone to have issues with water in your tank due to condensation.
That said, I live in new england and have your shared mindset, and have never had problems - although I don't drive really old cars... about 10 years generally. Older cars might be more likely to be affected.

mikeBOS · Post by **mikeBOS** » Wed Mar 23, 2011 12:25 am

"I think most people feel that driving is a necessity and so they are hyper concerned when costs that the *have* to pay go up. You can *choose* to buy a $4 latte, for some people they feel they can't choose not to drive."
I think this is really insightful.

Freedom_2018 · Post by **Freedom_2018** » Wed Mar 23, 2011 1:10 am

Probably same people who at the end of the tax year feel happier getting a tax refund versus being breakeven or owing some

dragoncar · Post by **dragoncar** » Wed Mar 23, 2011 3:11 am

I've also heard that when you let the fuel get too low, you increase the concentration of sludge going into your engine. Not sure if I buy that.
I've never paid much attention to how much I pay at the pump. I do, however, pay attention to how much I drive and the price of fuel. Trying to time purchases never made much sense to me given the small amounts we are discussing. It seems like you might as well be investing in oil futures if you really think you know how prices will change over time.

KevinW · Post by **KevinW** » Wed Mar 23, 2011 5:55 am

@dragoncar I don't buy the sludge thing either. There's a fuel filter that's supposed to block sludge.
I second Jacob's suggestion of avoiding a totally empty tank as a "be prepared" measure. If you ever drain your battery and get a jumpstart you'll be happy that you can drive home without needing to stop the car to refuel. Also you can use a running car as a generator or heater in a pinch.
Beyond that, I agree that frequent refueling is irrational.

Piper · Post by **Piper** » Wed Mar 23, 2011 2:44 pm

I drive a scooter. Whenever I go to the gas station people there make comments about how much cheaper it is for me (I filled up with $7 the other day.) Sometimes they think that I don't have to go to the gas station very often. With only a 2 gallon tank, I have to go a lot more often than they think. Also, I think something so small should get better than 62 miles per gallon. Fortunately, I don't drive my scooter or my car very much. My scooter once or twice a week and my car a few times a year. It really is good to live close to your job and your grocery store. What's really irrational isn't fueling up in bits and pieces it's being so dependent on your car to get around. Most car trips average only 3 miles. That's those little trips people make, not their commutes to work.

JohnnyH · Post by **JohnnyH** » Wed Mar 23, 2011 3:52 pm

I used to hit the pump up to 8 times a day for a couple bucks each time back in the rewards checking account heydays.

Got to wonder why more gas dependent people (or small businesses) don't work out some kind of gas hedging plan... But that would be light years from the "it's cheaper if I only put a couple bucks in" mindset.

George the original one · Wed Mar 23, 2011 4:03 pm

As a devotee of older cars, I can tell you that fuel filters clog with crap from fuel tanks that have rusted or where the cars have been used in dusty climates. In-tank fuel pumps are a pain in the posterior to change when their little filter socks clog with that crap and/or the pump fails because the crap got past the filter sock.
So, in short, yes it's true that keeping the tank full will reduce the odds of having to deal with crap in the fuel line. Usually not something you have to deal with in the first ten years of a car's life... it's the second & third & fourth decades where this issue rears up and bites you, usually when you're not the original owner and have no foreknowledge of how long the car sat with an empty tank before you bought it.

dragoncar · Post by **dragoncar** » Wed Mar 23, 2011 11:06 pm

Piper: "Most car trips average only 3 miles." -- I wonder if this is due to all those trips from one end of the parking lot to the other when visiting a strip mall.
JohnnyH: "I used to hit the pump up to 8 times a day for a couple bucks each time back in the rewards checking account heydays."
That reminds me of this awesome deal I got from Discover one time. It was a balance transfer with 0% interest forever, with the requirement that I make two purchases a month. Now, this would normally be profitable for them because while the balance transfer was 0% interest, your two monthly purchases would accrue interest at some ungodly amount like 18%. They apply all payments first to your lowest-interest balances.
By visiting the gas station, I was able to make two $0.04 purchases a month (felt a little bad for the gas station possibly paying two $0.25 transaction fees, but I would also fill up on my normal card). It took a very long time for the interest on my $0.04 purchases to equal the 5% I was earning on my remaining balance transfer, even factoring in taxes. I think I made about $2k over something like 6 years. Eventually, though, the high-interest balance got bigger and the minimum payments paid down most of the original balance transfer amount.

SF · Post by SF » Fri Mar 25, 2011 12:40 am

Another reason to keep the tank full (if you needed one) - the fuel keeps the fuel pump from overheating and lubed. Keeping the tank at least a quarter full is good for the life of the pump.

dot_com_vet · Post by **dot_com_vet** » Fri Mar 25, 2011 1:25 am

People's behavior with gasoline prices are insane. The people that complain the most, continue to drive guzzlers. Duh!
My home uses far more energy than my car. But nobody bats an eye at their home energy consumption.